Temporal cues are critical for speech perception. Understanding how time-varying signals are transformed in the forebrain will be critical for understanding how the representations of biologically-relevant signals, such as speech, are created in the auditory cortex. The auditory thalamus is a critical checkpoint for all information that reaches the auditory cortex. Despite many decades of scientific investigation, its role has remained unknown. One key to understanding the role of the thalamus likely lies in its interactions with a closely related and mysterious structure known as the thalamic reticular nucleus (TRN). I hypothesize that the auditory thalamus acts as a temporal filter and that the filtering properties are actively modulated by the thalamic reticular nucleus (TRN) by controlling the firing mode, switching thalamocortical neurons between tonic and burst spiking. The proposed studies will address the impact the auditory thalamus has on ascending information with and without TRN stimulation as well as elucidate the mechanisms of thalamic temporal filtering of complex inputs. Using a recently developed brain slice preparation that contains intact projections from the inferior colliculus (IC), to the auditory thalamus (portions of both dorsal and ventral medial geniculate body, or MGB), to the AC we will systematically perturb the TRN to assess its impact on colliculo- thalamo-cortical transmission. We will use laser photostimulation, flavoprotein autofluorescence imaging and whole cell-patch clamp in this work to investigate the cellular mechanisms of the impact of the TRN on temporal filtering by the MGB. This work, if successful, will allow us to gain insights as to how the auditory system processes complex signals, and will impact future design of therapeutic strategies, such as prosthetic devices, for patients with hearing loss or other disorders of communication.